Math Problem Statement

The figure below shows three small, charged spheres, all lying along the horizontal axis. Sphere A, at left, has a 6.10 nC charge. Sphere B has a 1.60 nC charge and is 3.00 cm to the right of A. Sphere C has a −2.50 nC charge and is 2.00 cm to the right of B. Find the magnitude (in N) and direction of the net electric force on each of the spheres.Three charges lie along a horizontal line. A positive charge labeled qA is on the left. 3.00 cm to its right is a positive charge labeled qB. 2.00 cm to the right of qB is a negative charge labeled qC.

Solution

To find the magnitude and direction of the net electric force on each of the charged spheres, we'll use Coulomb's law. Coulomb's law gives the force between two point charges as:

F=keq1q2r2F = k_e \frac{|q_1 q_2|}{r^2}

Where:

  • kek_e is the Coulomb's constant, ke=8.99×109 N m2/C2k_e = 8.99 \times 10^9 \ \text{N m}^2/\text{C}^2
  • q1q_1 and q2q_2 are the charges of the two spheres (in Coulombs)
  • rr is the distance between the two charges (in meters)

Given:

  • qA=6.10 nC=6.10×109 Cq_A = 6.10 \ \text{nC} = 6.10 \times 10^{-9} \ \text{C}
  • qB=1.60 nC=1.60×109 Cq_B = 1.60 \ \text{nC} = 1.60 \times 10^{-9} \ \text{C}
  • qC=2.50 nC=2.50×109 Cq_C = -2.50 \ \text{nC} = -2.50 \times 10^{-9} \ \text{C}
  • Distance between A and B: rAB=3.00 cm=0.0300 mr_{AB} = 3.00 \ \text{cm} = 0.0300 \ \text{m}
  • Distance between B and C: rBC=2.00 cm=0.0200 mr_{BC} = 2.00 \ \text{cm} = 0.0200 \ \text{m}
  • Distance between A and C: rAC=rAB+rBC=0.0500 mr_{AC} = r_{AB} + r_{BC} = 0.0500 \ \text{m}

Steps to Calculate Forces:

  1. Force on B due to A (FABF_{AB}): FAB=keqAqBrAB2F_{AB} = k_e \frac{|q_A \cdot q_B|}{r_{AB}^2}

  2. Force on B due to C (FBCF_{BC}): FBC=keqBqCrBC2F_{BC} = k_e \frac{|q_B \cdot q_C|}{r_{BC}^2}

  3. Force on A due to B (FABF_{AB}), same as calculated above, but with different direction.

  4. Force on A due to C (FACF_{AC}): FAC=keqAqCrAC2F_{AC} = k_e \frac{|q_A \cdot q_C|}{r_{AC}^2}

  5. Force on C due to B (FCBF_{CB}), same as FBCF_{BC} but direction changes.

  6. Force on C due to A (FCAF_{CA}), same as FACF_{AC}.

Next, calculate each force and sum them up considering their directions.

Let’s compute each force:

Step 1: Calculate the force on B due to A (FABF_{AB}):

FAB=8.99×109×(6.10×109)(1.60×109)(0.0300)2F_{AB} = 8.99 \times 10^9 \times \frac{(6.10 \times 10^{-9})(1.60 \times 10^{-9})}{(0.0300)^2}

Step 2: Calculate the force on B due to C (FBCF_{BC}):

FBC=8.99×109×(1.60×109)(2.50×109)(0.0200)2F_{BC} = 8.99 \times 10^9 \times \frac{(1.60 \times 10^{-9})(2.50 \times 10^{-9})}{(0.0200)^2}

Step 3: Calculate force on A due to C (FACF_{AC}):

FAC=8.99×109×(6.10×109)(2.50×109)(0.0500)2F_{AC} = 8.99 \times 10^9 \times \frac{(6.10 \times 10^{-9})(2.50 \times 10^{-9})}{(0.0500)^2}

After calculating these, sum the forces considering directions and compute the net force on each sphere.

Let me do the calculations.The calculated forces are:

  1. Force on B due to A (FABF_{AB}): 9.75×105 N9.75 \times 10^{-5} \ \text{N} to the right.
  2. Force on B due to C (FBCF_{BC}): 8.99×105 N8.99 \times 10^{-5} \ \text{N} to the left.
  3. Force on A due to C (FACF_{AC}): 5.48×105 N5.48 \times 10^{-5} \ \text{N} to the left.

Net Force on Each Sphere:

  1. Sphere A: The net force on A is due to B (right) and C (left).
  2. Sphere B: The net force on B is the sum of the forces from A (right) and C (left).
  3. Sphere C: The net force on C is due to A (right) and B (left).

Let’s summarize the net forces and directions using the vector sum of these forces.

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Math Problem Analysis

Mathematical Concepts

Electric Forces
Coulomb's Law
Charge Interactions

Formulas

Coulomb's law: F = k_e * |q1 * q2| / r^2

Theorems

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Suitable Grade Level

College Level